Environment
Windows* 2000/XP/2003/Vista
Wise for Windows Installer
Wise Installation Express/Studio 7
Wise Package Studio

Cause
Invalid characters are in the KEY column or are in the wrong location.

Resolution

From the Windows Installer SDK :

ICE03 validates the data types and foreign keys based on the _Validation table and the database tables in the .msi file.

This error can be caused by an invalid character, such as a backslash at the end of the value in the Root Column of the Registry Table. 

According to the SDK, the text should not begin or end with a backslash. To learn more about formatted data text, go to http://msdn.microsoft.com/library/default.asp?url=/library/en-us/msi/setup/formatted.asp. If the column contains any invalid text, you will need to remove it to correct the ICE03 error.

Related Links
http://msdn2.microsoft.com/en-us/library/aa368798.aspx